Add "--out-xml=xyz.xml" option that dumps the output of all actions, and the test.jam information, to the given file. Changes are mostly from Dave.

[SVN r41167]

tools/build

@@ -1 +1 @@
-Subproject commit 7724214a2b491ed9429c1e44c145afabbbfbec3d
+Subproject commit 823d54698ba2f9c6ae45ecc2359fd9f0e27f93ee